Ceramic cores are widely used in the casting of metal components. See, e.g., U.S. Pat. Nos. 3,957,715 to Lirones et al and 4,221,748 to Pasco et al. The cores are typically made by molding a mixture of ceramic particles and a binder into a desired shape to form a green (unsintered) core, and then heating the core to a high temperature to drive off the binder and sinter the ceramic particles to each other, as described in U.S. Pat. No. 3,234,308 to Herrmann. Ceramics which are useful in making cores include simple oxides such as aluminum oxide (alumina) and silicon dioxide (silica), as well as complex oxides such as zirconium orthosilicate (zircon), aluminum silicate (mullite), and magnesium aluminate (spinel). Core properties are often optimized by incorporating a mixture of different types (i.e., compositions) of ceramic particles in the core. The particles are usually in the form of powders, although ceramic fibers can also be used to make cores, as described in U.S. Pat. No. 4,427,742 to Wilgoose et al and in commonly assigned pending U.S. patent application Ser. No. 018,113 to Roth. This patent application and the issued patents noted above are all incorporated by reference. Injection molding and transfer molding are two techniques which are widely used in the manufacture of cores.
Green cores are occasionally produced which have defects of one sort or another such as cracks or pits, and in many instances, it is more economical to discard such defective cores rather than to repair them. However, in some cases, core manufacturers would rather repair the cores. This invention relates to an economical method for repairing defective green cores.